Fix static method call on non-generic class-string returning ErrorType

- Static method calls on non-generic class-string (e.g. $class::foo() where $class is class-string) now return mixed instead of *ERROR*
- The root cause was that ClassStringType::getObjectTypeOrClassStringObjectType() returns ObjectWithoutClassType, which has hasMethod() returning maybe, causing filterTypeWithMethod() to return null
- Added check in StaticCallHandler: when the resolved type is a classless object type (from class-string), return MixedType instead of ErrorType
- New regression test in tests/PHPStan/Analyser/nsrt/bug-9844.php

Author: staabm

src/Analyser/ExprHandler/StaticCallHandler.php

@@ -335,14 +335,17 @@ public function resolveType(MutatingScope $scope, Expr $expr): Type
 				$staticMethodCalledOnType = TypeCombinator::removeNull($scope->getType($expr->class))->getObjectTypeOrClassStringObjectType();
 			}
 
+			$methodName = $expr->name->toString();
 			$callType = $this->methodCallReturnTypeHelper->methodCallReturnType(
 				$scope,
 				$staticMethodCalledOnType,
-				$expr->name->toString(),
+				$methodName,
 				$expr,
 			);
 			if ($callType === null) {
-				$callType = new ErrorType();
+				$callType = $staticMethodCalledOnType->isObject()->yes() && $staticMethodCalledOnType->getObjectClassNames() === []
+					? new MixedType()
+					: new ErrorType();
 			}
 
 			if ($expr->class instanceof Expr) {

tests/PHPStan/Analyser/nsrt/bug-9844.php

@@ -0,0 +1,17 @@
+<?php declare(strict_types = 1);
+
+namespace Bug9844;
+
+use function PHPStan\Testing\assertType;
+
+class HelloWorld
+{
+
+	/**
+	 * @param class-string $class
+	 */
+	public function sayHello(string $class): void
+	{
+		assertType('mixed', $class::foo());
+	}
+}